How do you find the axis of symmetry, graph and find the maximum or minimum value of the function #y=2x^2+x-21#?

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Answer 1 · 2018-07-16T06:38:50

The axis of symmetry is #x=-1/4#. The minimum value is at #(-1/4, -21.625)#

The axis of symmetry of the function

#f(x)=ax^2+bx+c#

is

#x=-b/2a#

The function is

#y=2x^2+x-21#

#a=2#

#b=1#

Therefore,

The axis of symmetry is

#x=-1/(2+2)=-1/4#

The minimum value is

#f(-1/4)=2*(-1/4)^2-1/4-21=1/8-1/4-21=-21.125#

The minimum value is at #(-1/4, -21.625)#

The graph is as following

graph{2x^2+x-21 [-45.93, 58.1, -34.35, 17.7]}